Preserve wrapped adapter import semantics through caches

[jnunemaker]

Summary

• delegate cache-wrapper imports to the wrapped adapter so custom import behavior remains intact
• after a successful wrapped import, invalidate per-feature entries for the union of features before and after import, plus the feature-list and get-all entries
• preserve exceptions and false results without cache invalidation

The wrapped adapter import completes before cache invalidation begins; the cache is not part of the wrapped adapter's transaction. Ordinary cache-backed writes are unchanged. Instrumented#import already follows the same delegation contract and needs no change.

Tests

• bundle exec rspec -r active_support spec/flipper/adapters/active_support_cache_store_spec.rb (99 examples, 0 failures)
• bundle exec rspec spec/flipper/adapters/instrumented_spec.rb (45 examples, 0 failures)
• bundle exec rspec spec/flipper/adapters/redis_cache_spec.rb (83 examples, 0 failures)
• bundle exec ruby -Itest test/adapters/redis_cache_test.rb (34 runs, 925 assertions, 0 failures)
• bundle exec ruby -Itest test/adapters/dalli_test.rb (34 runs, 925 assertions, 0 failures)
• bundle exec rake test (310 runs, 8,336 assertions, 0 failures)
• bundle exec rspec -r active_support --exclude-pattern spec/flipper/cli_spec.rb (3,074 examples, 0 failures; 162 pending service-specific ActiveRecord examples)

The unfiltered RSpec run reached 3,102 examples with only two unrelated existing CLI ANSI-color expectation failures in this local non-color environment.